It was the late, wonderful, Princess Diana who memorably complained, her marriage was a little crowded with three in the relationship.
This exemplary episode, full of bathos and pathos, predates that - although maybe the young Diana watched it?
Albert finds and courts a prospective wife at the Darby and Joan Club, something Harold views with disdain. Instead of bringing home an Ena Sharples lookalike, Albert's prospective wife is an elegant 42 year old....who it transpires, Harold dated and fraternised with prior to going off on National Service to Malaysia, after which it appears, they lost touch because her mother failed to pass on letters he sent.
Now widowed with three kids, it doesn't take long for the old embers to flow and glow, kissing while Albert is out calling a minicab. In the funniest line in the episode, Harold tells his father he and Mrs Goodlace have associated intimately in the biblical sense. 'What', says Albert 'I was only out for ten minutes!'
As the episode ends, she tells them they are already married...ie, to each other. And to cement the point, when she has slipped off, they go like an old married pair into the minicab on the way to the restaurant Albert had booked.
What lifts this comedy into drama is the cultural resonance, it's almost, but not quite, a tear-jerker. The acting and script are excellent.
In all good sitcoms, characters wishing to escape, whether from Nelson Mandela House in Peckham or Oil Drum Lane in Shepherds Bush, never make it - and never can make it.
The skill of Galton and Simpson is in making this reality funny rather than frustrating or irksome.
Jean Kent, a highly regarded British actress of the 1940''s and 50's plays Mrs Goodlace with understanding and humility.
Had she married either, the dynamic would have changed for the worst. Best she left them, eternally married together - to viewers like us, as well.